Microsomal particles, properties

Chemical Properties of Microsomal Particles from Pea Seedlings," Plant Physiol. Suppl. 32 xll (1957). ... 

Free informosomes also have been observed in the cytoplasm of cells of insect epidermis. In contrast to embryonic informosomes, they are very heterogeneous with respect to buoyant density (Katatos, 1968). Finally, free mRNP particles similar in properties to informosomes have been described in the membrane fraction of microsomes from rat brain. These particles have a heterogeneous distribution in a sucrose density gradient and a buoyant density of about 1.40 g/cm. In contrast to nuclear complexes they are not destroyed by deoxycholate treatment (Samec et al., 1968). The nature of these particles remain unclear. 

Several observations support the contention that cytosolic lipid-protein particles originate from membranes. In particular, they contain phospholipid with the same fatty acids, albeit in different proportions, found in phospholipid of corresponding microsomal membranes [3]. In addition, lipid-protein particles with essentially similar properties can be generated in vitro from isolated microsomal membranes under conditions in which phospholipid catabolism has been activated by the addition of Ca [2,3]. The finding that the particles contain high concentrations of free fatly acids and steryl and wax esters suggests that they are formed at specific... 

Proteins of various sizes are dispersed in milk serum. They are called micelles and consist mostly of calcium salts of casein molecules. Furthermore, milk contains lipoprotein particles, also called milk microsomes, which consist of the residues of cell membranes, microviUi, etc., as well as somatic cells, which are mainly leucocytes (10 /I of milk). Some of the properties of the main structural elements of milk are listed in Table 10.4. 

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